This invention relates to the field of guidance systems and, more specifically, to wireless guidance systems.
Guidance systems are used in the location and positioning of devices. Current guidance systems, however can be very expensive. In addition, guidance systems, which rely on satellites that are positioned at great distances, may result in inaccurate positioning information due to weakened or blocked signals. One such system is the Global Positioning System, which is a network of satellites that transmits information signals that when received and decoded, allows a receiver to know its position within a coverage area. Use of the GPS enables self-guided weapons to find targets.
Unfortunately, the GPS signals, which typically use 10 watt signals from satellites in an 11,000 nautical mile orbit, are easy to jam with low power, low cost jammers scattered around a target area. Assuming a large number jammers are used to defend a high value target, one by one destruction of the jammers would have a low payoff. This is because even if only a few jammers remain operational, they can still effectively jam the guidance systems of incoming weapons.
Accordingly, one solution for providing an anti-jamming countermeasure for a GPS guided device is to equip the GPS guided device with a number of antennas, which point a null in the antenna radiation pattern at the source of the jamming signal. Though somewhat effective, this approach can be expensive since the number of jammers that can be nullified is one less than the number of antenna elements. As such, the effectiveness of this approach is limited when a large number of jammers are being used.
The present invention overcomes the limitations of the prior art by providing a wireless means of guidance for devices by receiving signals from surrounding wireless base stations, which are ordinarily used for wireless voice and data communications, (e.g., cellular-type service) and determining a current position of a device using at least the information from the received signals.
A method for wireless guidance for a device in accordance with the present invention includes receiving signals from at least one wireless base station indicating at least a respective position thereof, determining the current position of the device using at least the information contained in the received signals, calculating a vector between the determined current position and a predetermined desired destination for the device, and making trajectory corrections, using the calculated vector, to the device""s current trajectory so as to guide the device to the desired destination. In addition to the information contained in the received signals, the guidance system may also use stored information, such as indications of the location, communication protocols and operating frequencies of the wireless base stations, as well as previous position information from an alternate guidance system, for determining a current position for the device. The method wireless guidance may further include communicating with at least one wireless base station to initiate the transmission of information from the at least one wireless base station. Such communication may be for the purpose of activating an alternate source of power for the contacted wireless base station in the event of an outage of primary power source power for the wireless base station.
Advantageously, the present invention may be employed as a backup guidance system for a primary guidance system, in that it may be adapted to determine a current position for the device in the event of a primary guidance system failure. For example, in a device employing a GPS based guidance system as the primary guidance system, the wireless means of guidance of the present invention would be used to provide further guidance for the device in response to a GPS failure such as GPS blackout, GPS blockage, or poor GPS signal to noise ratio.